Conventionally, recording devices of an inkjet system (henceforth referred to as “inkjet recording device”) are widely known as an inkjet recording device which can flexibly adapt to high mix, low volume demands. Inkjet recording devices record an image on a recording medium by ejecting ink from a nozzle provided at a surface of a recording head facing the medium and causing it to land on the medium to fix it thereto, and are characterized in that they need no plate making process unlike conventional image recording means such as photogravure or flexographic printing, thus being capable of simply and quickly adapting to low volume demands. They also have advantages of generating less noise and easily providing color image recording by using ink of multicolors.
In recent years, inkjet recording devices using a photo curable ink have become known as an inkjet recording device capable of adapting to various recording media (e.g., Patent Document 1). In such inkjet recording devices, a photo curable ink containing a photo initiator having a certain sensitivity to light such as ultraviolet light is ejected and lands on a recording medium, which is then irradiated with light to be cured and fixed to the medium. In such inkjet recording devices, ink cures by irradiation with light instantaneously after the landing of the ink; so they have less penetration and bleeding of ink into a recording medium and can record an image not only on plain papers but also on recording media having no ink receiving layer and therefore having no ink absorptivity such as plastic or metal.
One of such inkjet recording devices is an inkjet recording device 50 of a serial printing system as shown in FIG. 9, in which a recording head 51 is reciprocally scanned in a main scanning direction while a recording medium is being intermittently fed in a feeding direction to form an image. In such an inkjet recording device 50, an photo curable ink is ejected from the recording head 51 and lands on the recording medium, and then irradiated with light by a light irradiation device 52 to be cured, and such a scan is repeated multiple times to form an image.
However, in conventional inkjet recording devices 50, the moving direction in the main scanning direction of the recording head 51 and light irradiation device 52 is switched without changing their relative position, so that the interval of time after the landing of ink until the irradiation with light differs between in the forward and backward scanning directions of the recording head 51. That is, the time needed for curing the ink is different between in the forward and backward scanning directions of the recording head 51, resulting in difference in dot diameter and degree of dot joining, which in turn presents a problem because the hue or gloss of the recorded image differs between the main scanning directions.
In order to avoid the difference in the hue or gloss of a recorded image between the main scanning directions, a technique is conventionally known in which two recording heads for ejecting ink of multiple colors are symmetrically disposed in the main scanning direction, thereby preventing difference in ink overlap between the forward and backward main scanning directions (e.g., Patent Document 2).
Also known is a technique of adjusting the amount of ink ejection in an inkjet recording device which records an image using an aqueous ink (e.g., Patent Document 3).
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2001-310454.
Patent Document 2: Japanese Patent No 3248704.
Patent Document 3: Japanese Unexamined Patent Application Publication No. 2003-25613.